October 11, 2005
Although the health effects of welding exposures often are difficult to predict, components of welding fumes have a range of toxicities that, under the right conditions, can affect many parts of the body adversely. Knowing what situations and welding process components can negatively impact your health is the first step toward learning how to protect yourself from those health hazards.
Increasing knowledge about the health hazards associated with breathing welding fumes and gases above certain concentrations and the serious illnesses that can result emphasizes the need to educate, train, and provide welders with appropriate protection.
Welding fumes are very fine, solid particles of metal oxides that form during the welding process. The specific substances and amount a welder inhales depend on the welding method, conditions under which the welding takes place, and the types of metals being welded. Many types of metals may be found in welding fumes, including arsenic, beryllium, cadmium, chromium, cobalt, copper, iron, lead, manganese, nickel, silicates, selenium, vanadium, and zinc.
Gases commonly associated with welding are carbon dioxide, carbon monoxide, nitrogen oxides, ozone, fluorine compounds, and phosgene. These gases may be present as the result of:
The health effects of welding fume exposures often are difficult to predict because the fumes contain a variety of substances in many concentrations. Components of welding fumes have a range of toxicities that, under the correct conditions, can affect many parts of the body adversely, including lungs, heart, kidneys, and central nervous system.
According to the American Welding Society (AWS) Fact Sheet #25, January 2002, exposure to excessive concentrations of welding fumes containing zinc, magnesium, copper, and cadmium may cause metal fume fever. Symptoms usually occur within four hours of exposure and include chills, fever, thirst, muscle ache, chest soreness, coughing, fatigue, nausea, and a metallic taste in the mouth. These flulike symptoms may last six to 24 hours, and complete recovery without intervention occurs within 24 to 48 hours.
Welding fumes also can irritate the eyes, nose, chest, and respiratory tract, causing coughing, shortness of breath, bronchitis, fluid in the lungs (pulmonary edema), and increased risk of pneumonia.
Studies indicate that welders may have up to a 30 percent to 40 percent increased risk of lung cancer as compared with other occupations.1However, the specific cause of this increased risk remains elusive. Confounding factors include high rates of smoking among welders and frequent exposure to asbestos and silica. The most likely cancer-causing components of welding fumes are hexavalent chromium and nickel. Another possible contributor is inhaling thorium particles while grinding thoriated tungsten electrodes.
Documented chronic respiratory ailments associated with overexposure to welding fumes include bronchitis, asthma, pneumonia, emphysema, and siderosis (caused by iron oxide dust in the lungs). In addition, evidence may link welding fumes to heart disease, skin diseases, ulcers, kidney damage, hearing loss, and reproductive problems. Welders also may have an increased risk of silicosis resulting from exposure to crystalline silica during secondary operations such as grinding and sanding.
One of the more recent ailments identified by the National Institutes of Health that can afflict welders is manganism, also known as welder's disease. Manganese is added to most steel to promote hardness. Inhaling manganese has been linked to weakness/lethargy, speech and psychological disturbances, paralysis, and tremors.
Another area receiving attention today is exposure to hexavalent chromium from welding stainless steel. Fluxes used in shielded metal arc welding (SMAW) and flux-cored arc welding (FCAW) tend to increase the amount of hexavalent chromium relative to the total chromium fume produced. Studies of workers in chromate production, plating, and pigment industries consistently show increased rates of lung cancer. The compound also has been linked to permanent eye damage, skin rashes, and ulcers.
The Occupational Safety and Health Administration (OSHA) proposed a standard in October 2004 that would reduce the exposure limit for hexavalent chromium to 1 microgram per cubic meter of air (g/m3), down from the current limit of 52 g/m3. The final standard is expected early in 2006.
Before beginning any welding job, it's critical to identify potential respiratory hazards particular to that operation. Fume exposure will depend on the following factors:
Good engineering controls and work practices are imperative. For example, it's important, when feasible, to use local and source-exhaust ventilation to remove harmful fumes and gases. Where possible, less hazardous materials should be substituted.
In many cases, engineering controls alone can't reduce exposure levels adequately. In such cases, it may be appropriate to use respirators. For any particular welding application, an array of respirator types that provide an appropriate level of protection are available. The unit cost of these respirators may be from around $1 for a basic negative-pressure, disposable, filtering facepiece to $1,000 or more for a positive-pressure system.
But the initial price is only one part of the equation. It's also important to consider that:
Heat stress is a common problem in welding and other metal fabrication operations. Heat stress may result in reduced productivity, reduced quality, increased risk of accidents, and higher employee turnover.
When heat stress is an issue, positive-pressure respirator systems employing vortex-cooling technology may be appropriate. To be used properly, these small, lightweight, belt-mounted devices require that breathing-quality air be supplied to the respirator from a remote compressor through an air hose. Air entering the headpiece can be lowered by up to 50 degrees F. Some systems provide heating when cold stress is an issue.
Clifford Frey is a certified industrial hygienist and senior technical service representative for 3M Occupational Health and Environmental Safety, 3M Center, Building 235-2E-91, St. Paul, MN 55144, 800-364-9577, email@example.com, www.mmm.com.
Note: 1. James M. Antonini, "Health Effects of Welding," Critical Reviews in Toxicology, Vol. 33, No. 1 (2003), pp. 61-103.
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